Typically, a computer system contains a processor, a bus, and other peripheral devices. The processor is responsible for executing instructions using data in the computer system. The bus is used by the processor and the peripheral devices for transferring information between one another. The information on the bus usually includes data, address and control signals. The peripheral devices comprise storage devices, input/output (I/O) devices, etc. Generally, all operations being performed in the computer system occur at the same frequency.
Many computer systems today employ a READY signal to terminate transfers on the bus. In such systems, the READY signal is an input to the processor and signifies to the processor whether the bus is available for another transfer. If a transfer is occurring on the bus or another peripheral device has control of the bus, the READY signal is not asserted until the transfer is complete. Once the transfer has been completed, the READY signal is asserted so that the processor knows that the bus is available. Typically system logic is responsible for controlling the state of the READY signal.
Reducing power consumption is an important concern with many modern personal computers. The reduction of power consumption is particularly significant with respect to battery-powered laptop or notebook style personal computers. By reducing power consumption, the battery life can be extended. These computer systems are often equipped with power management capabilities to reduce power consumption. These power management capabilities usually include the ability to reduce power consumption when a portion of the computer system is not being used or has not been used for some specific period of time.
Power management capabilities are also integrated into the integrated circuit devices themselves. Such devices include capabilities to monitor their activity, and may include monitoring their pins. If the device reaches a predefined set of inactivity, the device is able to place itself in a reduced power consumption state. When conditions or signals change, they are able to return to full power. Power use may be reduced in the portion of the device by turning off that portion of circuitry, by disabling power to the circuitry, or preventing that circuitry from receiving its regular clocking. The powered-down portion may be returned to full activity in response by enabling its power and/or clock. Although these devices and peripherals are equipped with power management capabilities, the operation of the power management capabilities is usually in response to a defined set of criteria. That is, only when the predefined criteria have been met, the power management capabilities are employed.
Sometimes, additional power savings is needed. For instance, if the voltage level of the battery supplying power to the computer system becomes low, additional power savings may be required to extend its battery life. Also, there may be a need to provide thermal management to the computer system where the temperature of the computer system is approaching or exceeding a maximum operating range. In such a case, it may be necessary to reduce power consumption to reduce the temperature of the computer system. If the computer system employs devices and peripherals with their own power management capability, these devices may not be able to provide the additional power management needs if their predefined criteria has not been met. The system designer could provide hardware in the computer system which is able to supply additional power management support. However, the requirement of additional devices or peripheral in the computer system typically results in higher costs. Therefore, it may be desirable to utilize the already existing power management capabilities of the devices in the computer system to achieve additional power savings for the computer system.
The present invention provides for reducing power consumption in a computer system. The computer system of the present invention incorporates devices that include power management capabilities. The present invention controls these devices to manipulate their power management capabilities. By doing so, the present invention is able to provide additional power savings beyond that normally designed for the device itself.